(1) Field of the Invention
The present invention relates to organic EL display apparatuses and methods of fabricating organic EL display apparatuses, and particularly relates to an active-matrix organic EL display apparatus and a method of fabricating the active-matrix organic EL display apparatus.
(2) Description of the Related Art
An image display apparatus using organic EL devices (organic EL display) has been known as an image display apparatus using current-driven light-emitting devices. The organic EL display has been attracting attention as a possible next-generation Flat Panel Display (FPD) for its advantages including wide viewing angles and small power consumption.
In an organic EL display, the organic EL devices composing pixels are usually arranged in a matrix. An organic EL display in which organic EL devices are provided at cross-points of row electrodes (scanning lines) and column electrodes (data lines), and the organic EL devices are driven by applying voltage corresponding to data signal between a selected row electrode and column electrodes is referred to as a passive-matrix organic EL display.
In contrast, an organic EL display in which thin film transistors (TFT) are provided at cross-points of the scanning lines and the data lines, a gate of a driving transistor is connected to the TFT, the data signal input is provided to the driving transistor by turning on the TFT through the selected scanning line, and the organic EL devices are driven by the driving transistors. Such an organic EL display is referred to as an active-matrix organic EL display.
In contrast with the passive-matrix organic EL display in which the organic EL devices connected to each row electrode (scanning line) emit light only when the row electrode is selected, in the active-matrix organic EL display, the organic EL devices can emit light until next scanning (selection). Accordingly, even when the duty cycle increases, the luminance of the display does not decrease. Thus, the display can be driven by low voltage, reducing the power consumption. However, due to variation in the characteristics of the driving transistors and the organic EL devices, the active-matrix organic EL display has a disadvantage that the luminance is uneven because luminance of the organic EL device in each pixel is different even when the same data signal is given.
Typical methods of compensating the unevenness in luminance due to variation in the characteristics (hereafter referred to as uneven characteristics) of the driving transistors and organic EL device caused by the fabricating process in the conventional organic EL display include compensation by complex pixel circuits and compensation using an external memory.
However, the complex pixel circuits decreases yield. In addition, the complex pixel circuits do not compensate the unevenness in the light-emitting efficiency of the organic EL device in each pixel.
For the reasons described above, several methods of compensating the unevenness in the characteristics of the pixels by the external memory have been proposed.
For example, according to the electric optical device, the method of driving the electric optical device, the method of fabricating the electric optical device, and the electronic device according to Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2005-283816, in a current program pixel circuit, the luminance of each pixel is measured by at least one type of input current, and the measured luminance ratio of each pixel is stored in the storage capacitance, the image data is corrected based on the luminance ratio, and the current program pixel circuit is driven by the image data after the correction. With this, the unevenness in luminance is suppressed, allowing a uniform display.